There should be little doubt that a person could be beaten to death with a helmet, or that a jugular vien could be torn open with a pen.
These were not designed to be used as such, therefore do no constitute a classification of "deadly weapon".
Using the Cap Police "logic", a deadly weapon could be anything used to kill, which means all of us carry deadly weapons. Lots of people have been punched and kicked to death. So I guess we're born with "deadly weapons" attached to our bodies.